(r5) DCacheStorageElement < Computing/Documentation

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---+ The PPD dCache Storage Element

DCache is the main disk storage system in us on the PPD Unix/Linux systems. It allows us to aggregate the storage space on many servers and present this as a unified namespace to users. Files in dCache can be accessed/written using the SRM "grid" protocol or the "local" protocols dcap and xrootd. The dCache namespace can also be browsed like a normal filesystem on the PPD linux nodes but the contents of the files cannot be accessed through this (i.e. ls or find will work cp, open or mv will fail).

VOs and/or groups have area to store files under their name dCache namespace in /pnfs/pp.rl.ac.uk/data/

---++ Inspecting a file using the pnfs mount

---++ Copying/Reading a file using the Grid tools

To copy a file into dCache without registering it in a Logical File Catalogue

lcg-cp -v file:/path/to/local/file srm://heplnx204.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/put/file

To copy a file into dCache and register it with a Logical File Catalogue

...

---++ Reading a file using local protocols

copying a file out of dCache using dcap:

dccp dcap://heplnx209.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/your/file ./file

Access a file directly from dCache using root:

root dcap://heplnx209.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/your/file

-- Main.ChrisBrew / Main.RobHarper - 2010-03-02
Topic revision: r5 - 2010-03-02 - RobHarper